Substrate cleaning apparatus

ABSTRACT

A substrate cleaning apparatus cleans a surface of a substrate such as a semiconductor wafer and dries the substrate. The substrate cleaning apparatus includes a process chamber having a substrate conveying unit configured to hold a substrate horizontally with its upper surface facing upwardly and to convey the substrate in one direction, and a cleaning unit configured to clean the surface of the substrate in non-contact state by supplying a cleaning liquid to the surface of the substrate which is moving in the process chamber. The substrate apparatus has an inert gas blowing unit configured to blow an inert gas toward the front and reverse surfaces of the substrate which has been cleaned in the cleaning unit to produce an inert gas atmosphere in the process chamber while drying the substrate with the inert gas.

CROSS REFERENCE TO RELATED APPLICATIONS

This document is a Continuation Application of U.S. application Ser. No.13/896,084, filed on May 16, 2013, which claims priorities to JapanesePatent Application Number 2012-113280, filed May 17, 2012 and JapanesePatent Application Number 2013-92632, filed Apr. 25, 2013, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a substrate cleaning apparatus forcleaning a surface of a substrate such as a semiconductor wafer anddrying the substrate, and more particularly to a substrate cleaningapparatus which can deal with a large semiconductor wafer having adiameter of 450 mm, and can clean a surface of a substrate efficientlyafter a polishing process such as CMP and dry the substrate.

Description of the Related Art

For example, in a damascene interconnect forming process for forminginterconnects by filling a metal into interconnect trenches formed in aninsulating film on a surface of a substrate, an extra metal on thesurface of the substrate is polished away by chemical mechanicalpolishing (CMP) after the formation of damascene interconnects. Aresidue of a slurry (slurry residue) that has been used in polishing,metal polishing debris and the like exists on the surface of thesubstrate after polishing. Therefore, it is necessary to remove theresidues (particles) remaining on the surface of the substrate afterpolishing.

As a substrate cleaning method for cleaning a surface of a substrateafter polishing, there has been known a roll scrub cleaning method forcleaning a surface of a substrate, such as a semiconductor wafer, with along cylindrical roll cleaning member (roll sponge or roll blush)extending horizontally by rotating the substrate and the roll cleaningmember while keeping the roll cleaning member in contact with thesurface of the substrate in the presence of a cleaning liquid. Thesubstrate which has been cleaned is generally rinsed by pure water (DIW)or the like, and is then spin-dried by rotating the substrate at a highspeed, as disclosed in Japanese laid-open patent publication No.11-340184.

In a substrate cleaning apparatus for cleaning a substrate such as asemiconductor wafer in the presence of a cleaning liquid while thesubstrate is rotated, it is difficult to process (clean) an entiresurface of the substrate uniformly because of different flow velocitiesof the cleaning liquid, different thicknesses of liquid films anddifferent temperatures of the cleaning liquid at respective portionssuch as a central portion, an edge portion, and the like of thesubstrate surface. Further, in the case where the substrate surfacehaving an exposed low-dielectric constant film (low-k film) serving asan insulating film is cleaned, because the low-k film is hydrophobic,non-uniformity of water wetting properties of the substrate surface isincreased and uniform cleaning over the entire surface of the substratebecomes further difficult. Particularly, when a surface of a largesubstrate such as a semiconductor wafer having a diameter of 450 mm iscleaned, this tendency becomes prominent.

Recently, copper has been used as interconnect metal. When copper isbrought into contact with a liquid such as pure water containing noanticorrosive, the copper becomes eroded easily by oxygen contained inthe liquid such as pure water, resulting in reliability degradation incopper interconnects and a decrease in product yield due toshort-circuit or open-circuit of the copper interconnects. Therefore, itis desirable that when the substrate surface having the exposed copperis cleaned, corrosion of copper caused by oxygen contained in the liquidsuch as pure water should be prevented as much as possible. Even if purewater or the like having a small amount of dissolved oxygen is used,corrosion of the copper surface caused by dissolution of oxygen in theair into pure water or the like may occur when the substrate surface iscleaned (rinsed) by supplying pure water or the like.

In order not to take oxygen in the air into pure water or the like whichhas no anticorrosive and is used for cleaning the substrate surface, itis considered that the substrate surface is cleaned in an inert gasatmosphere. However, in the substrate cleaning apparatus for cleaningthe substrate such as a semiconductor wafer in the presence of thecleaning liquid while the substrate is rotated, it is necessary toinstall a mechanism for holding the substrate and rotating thesubstrate. Therefore, in the case where a cleaning unit having suchmechanism is housed in a process chamber, the volume of the processchamber becomes considerably large. Thus, it is difficult to create adesired inert gas atmosphere in the process chamber.

As a substrate cleaning apparatus for cleaning a surface of a substratewithout rotating the substrate, there have been proposed a substratecleaning apparatus in which after polishing, a substrate is cleanedwhile the substrate is conveyed in one direction by a roller conveyer orthe like as disclosed in Japanese laid-open patent publication Nos.10-270392, 2002-217151 and 2006-73573, a substrate cleaning apparatus inwhich after polishing, a substrate is cleaned while the substrate isconveyed in non-contact state by a propulsive force of fluid jet asdisclosed in Japanese laid-open patent publication No. 2005-322936, anda substrate cleaning apparatus in which after polishing, a substrate iscleaned while the substrate is conveyed by a transport belt as disclosedin Publication No. 2001-501030 for Published Japanese translation of PCTInternational Publication No. WO98/08418.

Further, there have been proposed a substrate cleaning apparatus forcleaning a surface of a substrate by ejecting mist-like fluid (fluidmixture of gas and liquid) from a two-fluid nozzle to the surface of thesubstrate during conveyance of the substrate as disclosed in Japaneselaid-open patent publication Nos. 2006-247618 and 2010-118644, and asubstrate cleaning apparatus for cleaning a surface of a substrate in astore room filled with an inert gas such as nitrogen gas in order toprevent oxidation or reforming of the processed surface of the substrateas disclosed in Japanese laid-open patent publication No. 2004-22940.

The applicant of the present invention has proposed a substrateprocessing apparatus having at least one of an ultrasonic cleaningapparatus for cleaning a surface of a substrate by ultrasonic wavespropagated through a liquid and a two-fluid jet cleaning apparatus forcleaning the surface of the substrate by two-fluid jet comprising afluid mixture of gas and liquid as disclosed in International PatentPublication No. WO 2007/108315.

SUMMARY OF THE INVENTION

However, the conventional substrate cleaning apparatus cannot satisfyboth of the requirements for cleaning an entire surface of the substrateuniformly even if the substrate has a hydrophobic surface and has alarge diameter and for preventing corrosion of copper, used forinterconnect metal, caused by contact of copper with pure water or thelike as much as possible.

The present invention has been made in view of the above. It istherefore an object of the present invention to provide a substratecleaning apparatus which can clean an entire surface of the substrateuniformly even if the substrate has a hydrophobic surface and has alarge diameter, and can prevent corrosion of copper, used forinterconnect metal, caused by contact of copper with pure water or thelike as much as possible by a relatively simple structure.

In order to achieve the above object, according to one aspect of thepresent invention, there is provided a substrate cleaning apparatuscomprising: a process chamber having a substrate conveying unit thereinconfigured to hold a substrate horizontally with its upper surfacefacing upwardly and to convey the substrate in one direction; a cleaningunit configured to clean the surface of the substrate in non-contactstate by supplying a cleaning liquid to the surface of the substratewhich is moving in the process chamber; and an inert gas blowing unitconfigured to blow an inert gas toward the front and reverse surfaces ofthe substrate which has been cleaned in the cleaning unit to produce aninert gas atmosphere in the process chamber while drying the substratewith the inert gas.

According to the present invention, in the process chamber, while thesubstrate is conveyed in a sliding manner in one direction, the cleaningliquid is supplied to the surface of the substrate to clean the surfaceof the substrate in non-contact state. Thus, the cleaning liquid issupplied uniformly over the entire surface including the edge portion ofthe substrate, and the entire surface of the substrate can be cleaneduniformly and efficiently even if the substrate has a hydrophobicsurface and has a large diameter. Further, it is not necessary to rotatethe substrate during cleaning, and thus the volume of the processchamber can be diminished. Thus, the inert gas used to dry the substratecan be effectively utilized to produce a desired inert gas atmosphere inthe process chamber where corrosion of copper, used for interconnectmetal, caused by contact of copper with pure water or the like can beprevented as much as possible.

In a preferred aspect of the present invention, a flow of the inert gastoward inlet side of the process chamber is formed by blowing the inertgas toward the front and reverse surfaces of the substrate from theinert gas blowing unit.

According to the present invention, while air is prevented from flowinginto the process chamber through the inlet of the process chamber, theinert gas atmosphere can be produced in the process chamber.

In a preferred aspect of the present invention, the inert gas comprisesN₂ gas or Ar gas, and the inert gas atmosphere in the process chambercomprises an atmosphere having an oxygen concentration of 2% or less.

According to the present invention, by using N₂ gas or Ar gas as theinert gas to produce an inert gas atmosphere in the process chamberhaving an oxygen concentration of 2% or less, preferably 1% or less,oxygen contained in the air in the process chamber can be prevented frombeing taken into pure water or the like ejected toward the substrate.

In a preferred aspect of the present invention, the cleaning unitcomprises at least one of a two-fluid jet cleaning unit configured toclean the surface of the substrate with two-fluid jet stream comprisinga fluid mixture of gas and liquid and an ultrasonic cleaning unitconfigured to clean the surface of the substrate with ultrasonic wavespropagated in liquid.

According to the present invention, by cleaning the surface of thesubstrate by the two-fluid jet cleaning unit and/or the ultrasoniccleaning unit, minute particles remaining on the surface of thesubstrate which are difficult to remove by scrub cleaning can beremoved.

In a preferred aspect of the present invention, the substrate conveyingunit comprises a roller conveyer having a plurality of rollers spacedfrom each other, and a cleaning liquid supply nozzle configured tosupply a cleaning liquid to the reverse surface of the substrate isdisposed at the upstream side of the inert gas blowing unit.

According to the present invention, in the process chamber, while thesubstrate is conveyed in a sliding manner in one direction, a cleaningliquid such as pure water or the like is supplied to the reverse surfaceof the substrate to clean (rinse) the reverse surface.

In a preferred aspect of the present invention, the inert gas blowingunit comprises at least one air knife configured to blow the inert gasin the form of a sheet to the substrate.

According to the present invention, the inert gas in the form of a sharpknife is blown toward the front and reverse surfaces of the substrate,and thus the substrate can be dried more quickly and the flow of theinert gas formed in the process chamber and flowing toward the inletside of the process chamber can be accelerated in its flow velocity.

In a preferred aspect of the present invention, the substrate cleaningapparatus further comprises a bevel cleaning chamber coupled to theinlet of the process chamber and having a bevel cleaning unit configuredto clean the bevel portion of the substrate therein.

According to the present invention, cleaning of the bevel portion of thesubstrate after polishing, cleaning of the surface of the substrate anddrying of the substrate can be successively performed.

In a preferred aspect of the present invention, the bevel cleaning unitis configured to clean the bevel portion of the substrate while holdingthe substrate horizontally and rotating the substrate, and to transferthe substrate to the substrate conveying unit while holding thesubstrate horizontally.

According to the present invention, while the substrate is heldhorizontally, cleaning of the bevel portion of the substrate afterpolishing, cleaning of the surface of the substrate and drying of thesubstrate can be successively performed.

According to the substrate cleaning apparatus of the present invention,even if a substrate has a hydrophobic surface and has a large diameter,the entire surface of the substrate can be cleaned uniformly andefficiently. Further, by a relatively simple structure which utilizes aninert gas effectively to dry the substrate, corrosion of copper, usedfor interconnect metal, caused by contact of copper with pure water orthe like can be prevented as much as possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a substrate cleaning apparatus accordingto an embodiment of the present invention;

FIG. 2 is a sectional elevational view of the substrate cleaningapparatus shown in FIG. 1;

FIG. 3 is a schematic plan view showing an entire structure of apolishing apparatus having a substrate cleaning apparatus according toanother embodiment of the present invention;

FIG. 4 is a plan view showing the substrate cleaning apparatus providedin the polishing apparatus shown in FIG. 3;

FIG. 5 is a sectional elevational view showing the substrate cleaningapparatus shown in FIG. 4 together with a cleaning liquid supply system;and

FIG. 6 is an enlarged plan view showing an essential part of a bevelcleaning unit of the substrate cleaning apparatus provided in thepolishing apparatus shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A substrate cleaning apparatus according to embodiments of the presentinvention will be described below with reference to FIGS. 1 to 6.Identical or corresponding parts are denoted by identical referencenumerals in FIGS. 1 to 6, and will not be described in duplication.

FIG. 1 is a plan view showing a substrate cleaning apparatus accordingto an embodiment of the present invention. FIG. 2 is a sectionalelevational view of the substrate cleaning apparatus shown in FIG. 1. Asshown in FIGS. 1 and 2, the substrate cleaning apparatus comprises aninlet roller conveyer 10 and an outlet roller conveyer 20, and a processchamber 40 disposed between the inlet roller conveyer 10 and the outletroller conveyer 20 and having an inner roller conveyer 30 serving as asubstrate conveying unit therein. These roller conveyers 10, 20 and 30are configured to convey substrates horizontally in a sliding manner,with their front surfaces facing upwardly.

The inlet roller conveyer 10 has a plurality of rollers 12 disposed atpredetermined intervals in parallel with each other along a conveyancedirection of the substrate W, and the rollers 12 have respective shafts14 which are rotated in the same direction in synchronization with eachother. A plurality of wheels 16 are fixed to each shaft 14 atpredetermined positions along an axial direction of the shaft 14. Theoutlet roller conveyer 20 has a plurality of rollers 22 disposed atpredetermined intervals in parallel with each other along a conveyancedirection of the substrate W, and the rollers 22 have respective shafts24 which are rotated in the same direction in synchronization with eachother. A plurality of wheels 26 are fixed to each shaft 24 atpredetermined positions along an axial direction of the shaft 24.Similarly, the inner roller conveyer 30 serving as a substrate conveyingunit has a plurality of rollers 32 disposed at predetermined intervalsin parallel with each other along a conveyance direction of thesubstrate W, and the rollers 32 have respective shafts 34 which arerotated in the same direction in synchronization with each other. Aplurality of wheels 36 are fixed to each shaft 34 at predeterminedpositions along an axial direction of the shaft 34.

In this embodiment, the inlet roller conveyer 10, the outlet rollerconveyer 20 and the inner roller conveyer 30 are configured to constructa single roller conveyer. Specifically, the shafts 14 of the inletroller conveyer 10, the shafts 24 of the outlet roller conveyer 20, andthe shafts 34 of the inner roller conveyer 30 are configured to rotatein the same direction in synchronization with each other. Further, theheight (conveyer height) of the upper ends of the wheels 16 of the inletroller conveyer 10 from the floor surface, the height of the upper endsof the wheels 26 of the outlet roller conveyer 20 from the floorsurface, and the height of the upper ends of the wheels 36 of the innerroller conveyer 30 from the floor surface are set to be the same. Thus,the substrate W placed horizontally on the inlet roller conveyer 10 withits front surface facing upwardly is conveyed smoothly from the inletroller conveyer 10 to the inner roller conveyer 30 and from the innerroller conveyer 30 to the outlet roller conveyer 20.

In this embodiment, the process chamber 40 comprises a first cleaningchamber 42, a second cleaning chamber 44 and a drying chamber 46arranged in series along the conveyance direction of the substrate W.Each of the chambers 42, 44 and 46 has slit-like openings (not shown),for allowing the substrate W placed horizontally on the roller conveyers10, 20 and 30 to pass therethrough, at its inlet and outlet sides alongthe conveyance direction of the substrate W.

In this embodiment, a two fluid nozzle 50 serving as a two-fluid jetcleaning unit is disposed above the substrate W which is placed on theinner roller conveyer 30 in the first cleaning chamber 42 and conveyedhorizontally in a sliding manner by the inner roller conveyer 30. Thetwo-fluid nozzle 50 is directed downwardly to eject a two-fluid jetcomprising a fluid mixture of gas and liquid toward the surface (uppersurface) of the substrate, thereby cleaning the surface of the substratein non-contact state. The two-fluid nozzle (two-fluid jet cleaning unit)50 is connected to a carrier gas supply line (not shown) for supplying acarrier gas such as N₂ gas and a cleaning liquid supply line (not shown)for supplying a cleaning liquid such as carbonated water produced bydissolving CO₂ gas into pure water or ultrapure water. The two fluidnozzle 50 extends in a direction perpendicular to the conveyancedirection of the substrate W over the entire length of a diametricaldirection of the substrate W. The two-fluid nozzle 50 has a portextending linearly and continuously or ports provided intermittently atthe lower end thereof.

With this arrangement, the carrier gas such as N₂ gas and the cleaningliquid such as carbonated water supplied to the interior of thetwo-fluid nozzle 50 are ejected from the port (or ports) of thetwo-fluid nozzle 50 at a high speed to produce a two-fluid jet stream inwhich the cleaning liquid (carbonated water) exists as minute liquiddroplets (mist) in the carrier gas. Then, the two-fluid jet streamproduced by the two-fluid nozzle 50 is directed toward the surface ofthe substrate W and impinges on the surface of the substrate W which isplaced on the inner roller conveyer 30 and conveyed horizontally in asliding manner by the inner roller conveyer 30. Therefore, particles andthe like on the surface of the substrate W can be removed (cleaned) byutilizing impulse waves generated by impingement of the minute liquiddroplets on the surface of the substrate W. In this manner, since thescene of the substrate W is cleaned by the two-fluid jet stream ejectedfrom the two-fluid nozzle (two-fluid jet cleaning unit) 50, minuteparticles remaining on the surface of the substrate W which aredifficult to remove by scrub cleaning can be removed. This holds truefor the following ultrasonic cleaning unit 52.

The two-fluid nozzle (two-fluid jet cleaning unit) 50 produces atwo-fluid jet stream and enables the produced two-fluid jet stream toimpinge linearly on an area of the substrate W extending the entirelength of the substrate W in a diametrical direction of the substrate Wwhich is placed on the inner roller conveyer 30 and conveyedhorizontally in a sliding manner by the inner roller conveyer 30 withoutrotating the substrate W. Therefore, the two-fluid jet stream can besupplied uniformly over the entire surface including the edge portion ofthe substrate W, and the entire surface of the substrate W can becleaned uniformly and efficiently even if the substrate W has ahydrophobic surface and has a large diameter. Further, it is notnecessary to provide a rotating mechanism for rotating the substrate W,and thus the volume of the first cleaning chamber 42 for housing thetwo-fluid nozzle 50 therein can be greatly diminished.

It is preferable as a cleaning liquid to use carbonated water producedby dissolving CO₂ gas into ultrapure water which has been deaerated toremove oxygen therefrom. By using such carbonated water, the resistivityof the cleaning liquid can be lowered to prevent electrostatic dischargedamage of a surface of an object to be cleaned, for example, a surfaceof an insulating film.

In the present embodiment, an ultrasonic cleaning unit 52 for cleaningthe surface (upper surface) of the substrate W in non-contact state byutilizing ultrasonic waves propagated in a liquid such as pure water isdisposed above the substrate W which is placed on the inner rollerconveyer 30 in the second cleaning chamber 44 and conveyed horizontallyin a sliding manner by the inner roller conveyer 30. The ultrasoniccleaning unit 52 comprises a pair of liquid ejection nozzles 54 disposeddownwardly and spaced from each other for ejecting a liquid such as purewater toward the surface of the substrate W placed on the inner rollerconveyer 30 and conveyed horizontally in a sliding manner by the innerroller conveyer 30, and an ultrasonic transducer 56 disposed between theliquid ejection nozzles 54 for oscillating ultrasonic waves (megasonicenergy) of about 0.5 to 5.0 MHz, for example. These liquid ejectionnozzles 54 and the ultrasonic transducer 56 extend in a directionperpendicular to the conveyance direction of the substrate W over theentire length of the substrate in a diametrical direction of thesubstrate W. Each of the liquid ejection nozzles 54 has a port extendinglinearly and continuously or ports provided intermittently at the lowerend thereof.

With this arrangement, while a liquid such as pure water is ejected fromthe ports of the pair of the liquid ejection nozzles 54 toward thesurface of the substrate W placed on the inner roller conveyer 30 andconveyed horizontally in a sliding manner by the inner roller conveyer30, ultrasonic waves oscillated from the ultrasonic transducer 56 areapplied to the liquid accumulated on the surface of the substrate W toimpart acting forces by vibrational acceleration of liquid molecules toparticles and the like on the substrate of the substrate W. Thus, theparticles and the like on the surface of the substrate W can be removed(cleaned).

In the ultrasonic cleaning unit 52 also, as with the above two-fluidnozzle (two-fluid jet cleaning unit) 50, while a liquid such as purewater is supplied to the area extending over the entire length of thesubstrate W in a diametrical direction of the substrate W placed on theinner roller conveyer 30 and conveyed horizontally in a sliding mannerby the inner roller conveyer 30 without rotating the substrate W, theultrasonic waves are applied to the liquid. Therefore, the liquid towhich the ultrasonic waves are applied can be supplied uniformly overthe entire surface including the edge portion of the substrate W, andthe entire surface of the substrate W can be cleaned uniformly andefficiently even if the substrate W has a hydrophobic surface and has alarge diameter. Further, it is not necessary to provide a rotatingmechanism for rotating the substrate W, and thus the volume of thesecond cleaning chamber 44 for housing the ultrasonic cleaning unit 52therein can be greatly diminished.

As shown in FIG. 2, pure water ejection nozzles 60 and 62 may bedisposed upwardly to eject pure water toward the reverse surface (lowersurface) of the substrate W at at least one of locations between theadjacent rollers 32 below the substrate W placed on the inner rollerconveyer 30 in the first cleaning chamber 42 and the second cleaningchamber 44 and conveyed horizontally in a sliding manner by the innerroller conveyer 30. Therefore, the reverse surface of the substrate Wmay be cleaned (rinsed) by pure water ejected from at least one of thepure water ejection nozzles 60 and 62. The pure water ejection nozzles60 and 62 extend in a direction perpendicular to the conveyancedirection of the substrate W over the entire length of the substrate win a diametrical direction of the substrate W, and each of the purewater ejection nozzles 60 and 62 has a port extending linearly andcontinuously or ports provided intermittently at the upper end thereof.

In the illustrated embodiment, by using the inner roller conveyer 30serving as a substrate conveying unit and having the plural raters 32disposed at certain intervals in the process chamber 40, pure water canbe ejected toward the reverse surface (lower surface) of the substrate Wfrom the pure water ejection nozzles 60 and 62 disposed between therollers 32 to rinse the reverse surface of the substrate W.

Inside the drying chamber 46, there are provided a pair of air knives 64and 66 serving as an inert gas blowing unit configured to blow an inertgas such as N₂ gas or Ar gas toward the front and reverse surfaces ofthe substrate W. The air knives 64 and 66 are disposed above and belowthe substrate W placed on the inner roller conveyer 30 and conveyedhorizontally in a sliding manner by the inner roller conveyer 30. Eachof the air knives (inert gas blowing gas unit) 64 and 66 extends in adirection perpendicular to the conveyance direction of the substrate Wover the entire length of the substrate W in a diametrical direction ofthe substrate W. Thus, the inert gas such as N₂ gas or Ar gas is blownlinearly over the entire length of the substrate W in the diametricaldirection of the substrate W from the blowing ports of the air knives 64and 66 to thy the substrate W.

The air knives 64 and 66 are disposed so that the inert gas is blowntoward the front and reverse surfaces of the substrate W and flowstoward the inlet side of the process chamber 40 inside the processchamber 40. Specifically, the air knife 64 located above the substrateis disposed such that the air knife 64 extends obliquely downward toallow the blowing port at its lower end to be directed to the upstreamside of the conveyance direction of the substrate as it extendsdownwardly. The air knife 66 located below the substrate is disposedsuch that the air knife 66 extends obliquely upward to allow the blowingport at its upper end to be directed to the upstream side of theconveyance direction of the substrate as it extends upwardly.

Then, the inert gas such as N₂ gas or Ar gas is blown from the airknives 64 and 66 toward the substrate W to form a flow of the inert gassuch as N₂ gas or Ar gas toward the slit-like opening of the inlet sideof the process chamber 40. By this flow of the inert gas, air can beprevented from flowing into the process chamber 40. Thus, the interiorof the process chamber 40, i.e., the interiors of the first cleaningchamber 42, the second cleaning chamber 44 and the drying chamber 46 arekept in a certain inert gas atmosphere, for example, in an inert gasatmosphere having an oxygen concentration of 2% or less, preferably 1%or less.

As the inert gas blowing unit, the air knives 64 and 66 are used to blowthe inert gas in the form of a sharp knife toward the front and reversesurfaces of the substrate W, and thus the substrate W can be dried morequickly and the flow of the inert gas formed in the process chamber 40and flowing toward the inlet side of the process chamber 40 can beaccelerated in its flow velocity.

An inclination angle of blowing the inert gas from the air knives 64 and66 to the substrate is in the range of 0° to 30°, preferably 15° to 25°away from the vertical plane toward the inlet side of the processchamber 40. This inclination angle is determined from the twostandpoints of the drying capability of the substrate by the inert gasand the formation of the flow of the inert gas capable of stoppinginflow of the air through the inlet of the chamber.

As described above, in the first cleaning chamber 42 and the secondcleaning chamber 44, the surface of the substrate W conveyedhorizontally in a sliding manner can be cleaned without rotating thesubstrate W, and the reverse surface of the substrate W can be rinsedwith pure water, as needed. Therefore, the volumes of the first cleaningchamber 42 and the second cleaning chamber 44 can be diminished as muchas possible. Even in the drying chamber 46, since the substrate W can bedried without rotating the substrate, the volume of the drying chamber46 can be diminished as much as possible.

In this manner, by making the volumes of the first cleaning chamber 42,the second cleaning chamber 44 and the drying chamber 46, whichconstitute the process chamber 40, small as much as possible, the inertgas blown from the air knives 64 and 66 onto the substrate W to dry thesubstrate W can be effectively utilized to produce a desired inert gasatmosphere in the process chamber 40 where corrosion of copper, used forinterconnect metal, caused by contact of copper with pure water or thelike can be prevented as much as possible. Particularly, by producingthe inert gas atmosphere in the process chamber 40 having an oxygenconcentration of 2% or less, preferably 1% or less, oxygen contained inthe air in the process chamber 40 can be prevented from being taken intopure water or the like ejected toward the substrate W.

In the illustrated embodiment, the inlet roller conveyer 10, the outletroller conveyer 20, and the inner roller conveyer 30 in the processchamber 40 are driven, and the substrate W to be cleaned is placedhorizontally on the inlet roller conveyer 10. Then, the substrate Wplaced horizontally on the inlet roller conveyer 10 is conveyed in asliding manner to the first cleaning chamber 42 of the process chamber40, and the substrate W is cleaned by the two-fluid nozzle (two-fluidjet cleaning unit) 50 disposed in the first cleaning chamber 42.Thereafter, the substrate W is conveyed in a sliding manner from thefirst cleaning chamber 42 to the second cleaning chamber 44 of theprocess chamber 40, and the substrate W is ultrasonically cleaned by theultrasonic cleaning unit 52 disposed in the second cleaning chamber 44.After the cleaning, the substrate W is conveyed in a sliding manner tothe drying chamber 46, and the substrate W is dried by blowing the inertgas such as N₂ gas or Ar gas onto the substrate W from the air knives64, 66 disposed in the drying chamber 46 and is then conveyed to theoutlet roller conveyer 20. Thereafter, the dried substrate W is takenout from the outlet roller conveyer 20 and conveyed to a next process.

A series of cleaning and drying processes of the substrate W areperformed in a slide conveyance process in which the substrate W isconveyed from the inlet roller conveyer 10 to the inner roller conveyer30 of the process chamber 40 and then from the inner roller conveyer 30of the process chamber 40 to the outlet roller conveyer 20 withoutrotating the substrate W. Therefore, even if the substrate W has ahydrophobic surface and has a large diameter, the entire surface of thesubstrate W can be processed uniformly and efficiently.

Further, by producing the inert gas atmosphere in the process chamber 40having an oxygen concentration of 2% or less, preferably 1% or less,oxygen contained in the air in the process chamber 40 can be preventedfrom being taken into pure water or the like, containing noanticorrosive, ejected toward the substrate, and corrosion of copper,used for interconnect metal, caused by contact of copper with pure wateror the like can be prevented.

FIG. 3 is a schematic plan view showing an entire structure of apolishing apparatus having a substrate cleaning apparatus according toanother embodiment of the present invention. As shown in FIG. 3, thepolishing apparatus includes a substantially rectangular housing 70whose interior is divided by partition walls into a loading/unloadingsection 72, a first polishing section 74, a second polishing section 76and a cleaning section 78. The loading/unloading section 72, thepolishing sections 74, 76, and the cleaning section 78 are independentlyfabricated and independently evacuated.

The loading/unloading section 72 includes at least two (e.g., four inthis embodiment) front loading sections 80 on which substrate cassettesfor storing a number of substrate such as a semiconductor wafers areplaced. These front loading sections 80 are arranged side by side in awidth direction (direction perpendicular to the longitudinal direction)of the polishing apparatus. Further, in the loading/unloading section72, there is provided a transfer robot 82 on a moving mechanism (notshown) placed along the front loading sections 80 so that the transferrobot 82 is movable along the direction in which the substrate cassettesare arranged. The transfer robot 82 can access the substrate cassettesplaced on the front loading sections 80 by moving on the movingmechanism.

The loading/unloading section 72 is an area that needs to be kept in thecleanest environment. Accordingly, the interior of the loading/unloadingsection 72 is constantly kept at a higher pressure than any of theoutside of the apparatus, the polishing sections 74, 76 and the cleaningsection 78. Further, a filter-fan unit (not shown) having an air filter,such as an HEPA filter or a ULPA filter, is provided above the transferrobot 82. Clean air, from which particles, toxic vapor and toxic gashave been removed, is blown off downwardly at all times by thefilter-fan unit.

The first polishing section 74 is an area where the substrate ispolished, and has a first polishing unit 84 a and a second polishingunit 84 b therein. The second polishing section 76 is also an area wherethe substrate is polished, and has a third polishing unit 84 c and afourth polishing unit 84 d therein. These first polishing unit 84 a,second polishing unit 84 b, third polishing unit 84 c and fourthpolishing unit 84 d are arranged along the longitudinal direction of thepolishing apparatus.

The first polishing unit 84 a includes a polishing table 86 a having apolishing surface and a top ring 88 a for holding the substrate andpressing the substrate against the polishing table 86 a to polish thesubstrate. Similarly, the second polishing unit 84 b includes apolishing table 86 b and a top ring 88 b, the third polishing unit 84 cincludes a polishing table 86 c and a top ring 88 c, and the fourthpolishing unit 84 d includes a polishing table 86 d and a top ring 88 d.

A first linear transporter 90 is provided between the first polishingunit 84 a and the second polishing unit 84 b in the first polishingsection 74, and the cleaning section 78. This first linear transporter90 is configured to transfer substrates between four transferringpositions located along the longitudinal direction of the polishingapparatus (hereinafter, these four transferring positions will bereferred to as a first transferring position TP1, a second transferringposition TP2, a third transferring position TP3, and a fourthtransferring position TP4 in the order from the loading/unloadingsection 72). A reversing machine 92 for reversing a substratetransferred from the transfer robot 82 in the loading/unloading section72 is disposed above the first transferring position TP1 of the firstlinear transporter 90. A vertically movable lifter (not shown) isdisposed below the reversing machine 92. A vertically movable pusher(not shown) is disposed below the second transferring position TP2, anda vertically movable pusher (not shown) is disposed below the thirdtransferring position TP3.

In the second polishing section 76, a second linear transporter 94 isprovided next to the first linear transporter 90. This second lineartransporter 94 is configured to transfer substrates between threetransferring positions located along the longitudinal direction of thepolishing apparatus (hereinafter, these three transferring positionswill be referred to as a fifth transferring position TP5, a sixthtransferring position TP6, and a seventh transferring position TP7 inthe order from the loading/unloading section 72). A pusher (not shown)is disposed below the sixth transferring position TP6 of the secondlinear transporter 94, and a pusher (not shown) is disposed below theseventh transferring position TP7 of the second linear transporter 94.

As can be understood from the fact that a slurry is used duringpolishing, the polishing sections 74, 76 are the dirtiest areas.Therefore, in order to prevent particles from spreading out of thepolishing sections 74, 76, evacuation is conducted from surroundingspaces of the respective polishing tables in this embodiment. Inaddition, pressure in the interior of the polishing sections 74, 76 isset to be lower than any of pressure outside the apparatus, pressure inthe cleaning section 78, and pressure in the loading/unloading section72, so that scattering of particles is prevented. Typically, exhaustducts (not shown) are provided below the polishing tables, respectively,and filters (not shown) are provided above the polishing tables, so thatdownward flows of clean air are formed through the filters and theexhaust ducts.

The cleaning section 78 is an area where polished substrates arecleaned. The cleaning section 78 includes a reversing machine 96 forreversing a substrate and a substrate cleaning apparatus 100 forcleaning the polished substrates according to another embodiment of thepresent invention. The reversing machine 96 and the substrate cleaningapparatus 100 are arranged in series along the longitudinal direction ofthe polishing apparatus. A filter fan unit (not shown), having a cleanair filter, is provided above the substrate polishing apparatus 100.This filter fan unit is configured to remove particles from an air toproduce clean air, and to form downward flow of the clean air at alltimes. Pressure in the interior of the cleaning section 78 is kepthigher than pressure in the polishing sections 74, 76, so that particlesin the polishing sections 74, 76 are prevented from flowing into thecleaning section 78.

A swing transporter 102 is provided between the first linear transporter90 and the second linear transporter 94, and the reversing machine 96 ofthe cleaning section 78. The swing transporter 102 is configured totransfer a substrate from the fourth transferring position TP4 of thefirst linear transporter 90 to the fifth transferring position TP5 ofthe second linear transporter 94, from the fifth transferring positionTP5 of the second linear transporter 94 to the reversing machine 96, andfrom the fourth transferring position TP4 of the first lineartransporter 90 to the reversing machine 96, respectively.

FIGS. 4 through 6 show the detailed structure of the substrate cleaningapparatus 100 according to another embodiment of the present inventionshown in FIG. 3. As shown in FIGS. 4 through 6, the substrate cleaningapparatus 100 is different from the substrate cleaning apparatus shownin FIGS. 1 and 2 in that a bevel cleaning chamber 112 having a bevelcleaning unit 110 for cleaning a bevel portion therein is provided, inplace of the inlet roller conveyer 10. Other structures of the substratecleaning apparatus 100 is the same as the substrate cleaning apparatusshown in FIGS. 1 and 2. Specifically, in the substrate cleaningapparatus 100, the first cleaning chamber 42 of the process chamber 40is coupled to the bevel cleaning chamber 112, and the substrate W isprocessed (bevel-cleaned) in the bevel cleaning chamber 112, and is thentransferred to the inner roller conveyer 30 in the process chamber 40.While the substrate W is conveyed in a sliding manner from the innerroller conveyer 30 to the outlet roller conveyer 20, the substrate W isprocessed to clean the surface of the substrate and to dry thesubstrate.

The bevel cleaning unit 110 comprises a main guide rail 114 extendingalong the conveyance direction of the substrate W, a movable body 120movable along the main guide rail 114 and having a pair of arms 118whose forward ends have respective rotatable rollers 116, and anauxiliary guide rail 122 extending in parallel with the main guide rail114. With this arrangement, the substrate W is supported horizontally bythree points of the pair of the rollers 116 and the auxiliary guide rail122, and is conveyed toward the process chamber 40 by movement of themovable body 120 while the substrate W is horizontally rotated byrotation of the rollers 116. A groove is formed in each of the outercircumferential surfaces of the rollers 116 and a groove is formed in aside surface of the auxiliary guide rail 122 facing the substrate W.When the substrate W is supported by the three points of the pair of therollers 116 and the auxiliary guide rail 122, the edge portion of thesubstrate W is fitted into the grooves of the rollers 116 and theauxiliary guide rail 122 facing the substrate W to prevent the substrateW from dropping off.

When the substrate W is horizontally supported by the three points ofthe pair of the rollers 116 and the auxiliary guide rail 122, acylindrical bevel cleaning member 124 such as brush or sponge is fixedat the location of the movable body 120 facing the bevel portion of thesubstrate W so as to bring the outer circumferential surface of thecylindrical bevel cleaning member 124 in sliding contact with the bevelportion of the substrate W.

Above and below the substrate W supported horizontally by the threepoints of the pair of the rollers 116 and the auxiliary guide rail 122and conveyed horizontally in the bevel cleaning chamber 112, there areprovided a plurality of cleaning liquid supply nozzles 126 disposed atpredetermined positions along the longitudinal direction of thesubstrate cleaning apparatus 100 and having a plurality of ports 126 afor ejecting the cleaning liquid toward the front and reverse surfacesof the substrate W. Each of the cleaning liquid supply nozzles 126extend in a direction perpendicular to the conveyance direction of thesubstrate W over the entire length of the substrate Win a diametricaldirection of the substrate W.

Further, a cleaning liquid tank 128 for storing the cleaning liquidtherein is provided, and each of the cleaning liquid supply nozzles 126is connected to a cleaning liquid supply line 134 extending from thecleaning liquid tank 128 and having a pump 130 and a filter 132 thereon.Further, the bottom portion of the bevel cleaning chamber 112 and thecleaning liquid tank 128 are connected to each other by a cleaningliquid return line 136. With this arrangement, the cleaning liquidstored in the cleaning liquid tank 128 can be circulated and reused.

In the illustrated embodiment, the bevel cleaning unit 110 is configuredsuch that the cleaning liquid is ejected from the ports 126 of therespective cleaning supply nozzles 126, and the cleaning liquidcollected in the bottom portion of the bevel cleaning chamber 112 isrecovered by the cleaning liquid tank 128 and circulated. In this state,the polished substrate W is horizontally supported by the three pointsof the pair of the rollers 116 and the auxiliary guide rail 122 with itssurface facing upwardly, and conveyed horizontally toward the processchamber 40 by movement of the movable body 120 while the substrate W ishorizontally rotated by rotation of the rollers 116. Thus, the bevelportion of the substrate W is rubbed with the bevel cleaning member 124in the presence of the cleaning liquid, thereby scrub-cleaning the bevelportion of the substrate W. The cleaning liquid includes anticorrosive,and hence corrosion of copper as interconnect metal caused by contact ofthe substrate W with the cleaning liquid can be prevented.

After cleaning of the bevel portion of the substrate W, the substrate Wis transferred in its horizontal state to the inner roller conveyer 30in the process chamber 40 of the substrate cleaning apparatus 100. Aswith the substrate cleaning apparatus shown in FIG. 1, while thesubstrate W is conveyed horizontally in a sliding manner on the innerroller conveyer 30, the substrate W is cleaned and dried, and is thentransferred to the outlet roller conveyer 20. Thus, cleaning of thebevel portion of the substrate after polishing, cleaning of the surfaceof the substrate and drying of the substrate can be successivelyperformed.

Next, a process example of the substrate conducted by the polishingapparatus having the above structure will be described below.

An odd-numbered (1, 3, . . . ) substrate is taken out of the substratecassette of the front loading section 80 by the transfer robot 82, andthe substrate is transferred to the reversing machine 92. The substrateis reversed so as to become its front surface facing downwardly by thereversing machine 92, and then transferred to the second transferringposition TP2 of the first linear transporter 90. The substrate placed onthe second transferring position TP2 is held by the top ring 86 a of thefirst polishing unit 84 a and polished on the polishing table 88 a(first-step polishing), and is then returned to the second transferringposition TP2 and transferred to the third transferring position TP3. Thesubstrate placed on the third transferring position TP3 is held by thetop ring 86 b of the second polishing unit 84 b and polished on thepolishing table 88 b (second-step polishing), and is then returned tothe third transferring position TP3 and transferred to the fourthtransferring position TP4.

The substrate placed on the fourth transferring position TP4 is held bythe swing transporter 102 and conveyed to the reversing machine 96 ofthe cleaning section 78 by the swing transporter 102. The substrate isreversed to become its front surface facing upwardly. As describedabove, the reversed substrate is conveyed horizontally in the bevelcleaning chamber 112 of the substrate cleaning apparatus 100, and thebevel portion of the substrate is cleaned. After cleaning of the bevelportion, the substrate is horizontally conveyed in a sliding manner inthe process chamber 40 of the substrate cleaning apparatus 100, andcleaning of the surface of the substrate and drying of the substrate areconducted. Then, the substrate is transferred to the outlet rollerconveyer 20.

The cleaned and dried substrate on the outlet roller conveyer 20 is heldby the transfer robot 82 and returned to the substrate cassette of thefront loading section 80.

On the other hand, an even-numbered (2, 4, . . . ) substrate is takenout of the substrate cassette of the front loading section 80 by thetransfer robot 82, and the substrate is transferred to the reversingmachine 92. The substrate is reversed so as to become its front surfacefacing downwardly by the reversing machine 92, and then transferred tothe fifth transferring position TP5 of the second linear transporter 94through the first linear transporter 90 and the swing transporter 102,and further to the sixth transferring position TP6. The substrate placedon the sixth transferring position TP6 is held by the top ring 86 c ofthe third polishing unit 84 c and polished on the polishing table 88 c(first-step polishing), and is then returned to the sixth transferringposition TP6 and transferred to the seventh transferring position TP7.The substrate placed on the seventh transferring position TP7 is held bythe top ring 86 d of the fourth polishing unit 84 d and polished on thepolishing table 88 d (second-step polishing), and is then returned tothe seventh transferring position TP7 and transferred to the fifthtransferring position TP5.

The substrate placed on the fifth transferring position TP5 is held bythe swing transporter 102, and transferred to the reversing machine 96of the cleaning section 78. The substrate is reversed to become itsfront surface facing upwardly by the reversing machine 96. As describedabove, the reversed substrate W is conveyed horizontally in the bevelcleaning chamber 112 of the substrate cleaning apparatus 100, and thebevel portion of the substrate W is cleaned. After cleaning of the bevelportion, the substrate W is horizontally conveyed in a sliding manner inthe process chamber 40 of the substrate cleaning apparatus 100, andcleaning of the surface of the substrate and drying of the substrate areconducted. Then, the substrate is transferred to the outlet rollerconveyer 20.

Then, the cleaned and dried substrate on the outlet roller conveyer 20is held by the transfer robot 82 and returned to the substrate cassetteof the front loading section 80.

According to the polishing apparatus of the illustrated embodiment,while the substrate is held horizontally, cleaning of the bevel portionof the substrate after polishing, cleaning of the surface of thesubstrate and drying of the substrate can be successively performed.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made without departing from the scopeof the appended claims.

What is claimed is:
 1. A substrate cleaning method comprising: conveyinga substrate from an inlet of a process chamber into the process chamber;holding the substrate horizontally with its upper surface facingupwardly by a substrate conveying unit having a support member to conveythe substrate in one direction in the process chamber; cleaning frontand reverse surfaces of the substrate by a plurality of cleaning unitsprovided in the process chamber, the plurality of cleaning units beingarranged above and below the substrate conveying unit; drying thesubstrate by blowing an inert gas toward the front and reverse surfacesof the substrate from an inert gas blowing unit provided in a dryingunit while stopping air inflow through the inlet of the process chamberby a flow of the inert gas formed by the inert gas blowing unitextending in a direction perpendicular to a conveyance direction of thesubstrate and being arranged at a predetermined angle from a verticalplane toward the inlet side of the process chamber; wherein a blowingport of the inert gas blowing unit is directed to an upstream side ofthe conveyance direction of the substrate to form the flow of the inertgas toward the cleaning units; and wherein an inert gas atmosphere isproduced throughout the process chamber including the cleaning units andthe drying unit by blowing the inert gas from the inert gas blowingunit.
 2. The substrate cleaning method according to claim 1, wherein thesubstrate is conveyed in a sliding manner by the substrate conveyingunit comprising a plurality of rollers.
 3. The substrate cleaning methodaccording to claim 1, further comprising cleaning a bevel portion of thesubstrate by a bevel cleaning member fixed at a location facing thebevel portion of the substrate conveyed by the substrate conveying unitso as to be in sliding contact with the bevel portion of the substrate.